Method for obtaining information on food stuff in or for a cooking process

Abstract

The present invention relates to a method for obtaining information on food stuff in or for a cooking process comprising the steps of: a) detecting an electrical impedance (Z) or at least one component thereof in a, preferably inner, region of the food stuff, b) deriving from said detected impedance or component thereof information about the age or freshness of the food stuff, c) providing said information about the age or freshness to a user interface and/or to an information output unit and/or to a control unit for controlling the cooking process, in particular for adapting the cooking time and/or cooking temperature dependent on this information about the age or freshness.

1 . A method for obtaining information on food stuff in or for a cooking process comprising the steps of:
 a) detecting an electrical impedance (Z) or at least one component thereof in a, preferably inner, region of the food stuff;   b) deriving from said detected impedance or component thereof information about at least one characteristic property of the food stuff, the characteristic property of the food stuff being at least one of the type of food, the age or freshness, the content of fat, and whether the food was frozen before or not, of the food stuff;   c) providing said information about the characteristic property of the food stuff to a user interface and/or to an information output unit and/or to a control unit for controlling the cooking process.   
     
     
         2 . The method according to  claim 1 , comprising at least one (or an arbitrary combination) of the following steps:
 a) applying at least one electric voltage to said region of the food stuff and measuring the impedance (Z) or the at least one component thereof in that region of the food stuff,   b) using at least one food probe which is inserted into the food stuff and comprises at least two electrodes for applying the electric voltage and measuring the impedance (Z) or the at least one component thereof,   c) the at least one electrical component of the electrical impedance (Z) is chosen from the group comprising the ohmic resistance (R), the reactance (X), the capacity, the inductivity, the modulus and the phase angle (φ).   
     
     
         3 . The method according to  claim 1 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) deriving the information about the food type of the food stuff, including in particular different types of meat and/or fish and/or vegetables, from said detected impedance or component thereof before said step of deriving information about the age or freshness of the food stuff and/or based on the same detected impedance or component values as said step of deriving information about the age or freshness of the food stuff;   d) using said information about the characteristic property of the food stuff for adapting the cooking time and/or cooking temperature of the cooking process dependent on this information, wherein in particular for less fresh or aged food stuff and/or for food stuff already frozen before the cooking time is selected to be longer and/or the cooking temperature is selected to be higher or to be at a high level for a longer time.   
     
     
         4 . The method according to  claim 1 , comprising at least one or an arbitrary combination of the following steps or features:
 a) said step of deriving information about the characteristic property of the food stuff from said detected impedance or component thereof is performed by comparison with stored pre-determined reference data;   b) wherein in particular the reference data can be supplemented by the user.   
     
     
         5 . The method according to  claim 1 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) said step of detecting the electrical impedance (Z) or the at least one component thereof of the food stuff for a subsequent deriving of information on the characteristic property of the food stuff takes place before or at the beginning of the cooking process and/or in a predefined temperature range, preferably low, temperature e.g. room temperature;   b) in said step of detecting the electrical impedance (Z) or the at least one component thereof of the food stuff several values are measured in a pre-given time interval, e.g. several minutes, at pre-determined instants of time, e.g. every 10 to 60 seconds,   
     
     
         6 . The method according to  claim 1 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) detecting the electrical impedance (Z) or the at least one component thereof at one, two or more frequencies (f), in particular of the electric voltage applied;   b) wherein in particular, for n>1 frequencies, m measuring steps are performed with 0<m≦n in each of which a voltage is applied wherein each of the n frequencies is contained in at least one of the applied voltages;   c) one of the two different frequencies (f) is in particular chosen to be 50 kHz and another one of the two different frequencies (f) is chosen to be 5 kHz.   
     
     
         7 . The method according to  claim 6 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) comparing the detected values of the impedance or component thereof at the one, two or more frequencies with the same number of stored reference values for characteristic properties of food stuff previously determined at the same frequencies and determining the characteristic property of the food stuff by determining the highest degree of coincidence with the reference values, e.g. by some mathematical norm, for instance Euklidian norm, or metric;   b) using in said step of deriving of information on the characteristic property of the food stuff a function or calculation algorithm of the detected values of the impedance or component thereof at the one, two or more frequencies;   c) using in said step of deriving of information on the characteristic property of the food stuff a ratio of two detected values of the impedance or component thereof at two different frequencies;   d) using in said step of deriving of information on characteristic property of the food stuff a difference or sum of two detected values of the impedance or component thereof at two different frequencies;   d) using in said step of deriving of information on the characteristic property of the food stuff a ratio of a difference and the sum of two detected values of the impedance or component thereof at two different frequencies.   
     
     
         8 . The method according  claim 1 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) using in said step of deriving information about the characteristic property, in particular the age or freshness and/or the type, of the food stuff the ohmic resistance (R) as the component of the impedance;   the ohmic resistance (R) over the same frequency spectrum for different characteristic properties, in particular for different food types as well as for different food age, differs in absolute values as well as in the first derivative and the second derivative;   c) at lower frequencies, the ohmic resistance (R) of fresh food stuff, in particular meat such as poultry, is higher than that of aged food stuff and/or wherein the ohmic resistance (R) of fresh food stuff decreases more steeply with increasing frequency than that of aged food stuff and/or wherein, at high frequencies (f), the ohmic resistance (R) of the fresh food stuff is higher than that of aged food stuff and/or wherein the curve of the ohmic resistance for fresh food stuff has a turning point in contrast to aged food stuff.   
     
     
         9 . The method according to  claim 1 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) using in said step of deriving information about the characteristic property of the food stuff the reactance (X) as the component of the impedance;   b) the reactance over the same frequency spectrum for different characteristic properties, in particular for different food types as well as for different food age, differs in absolute values as well as in the first derivative and the second derivative; and   c) the reactance of fresh food stuff, in particular meat such as poultry, as well as of aged food stuff has a minimum in a given frequency spectrum and the reactance (X) of the fresh food stuff at the minimum is smaller than the reactance (X) of the aged food stuff at the minimum.   
     
     
         10 . The method according to  claim 1 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) using in said step of deriving information about the characteristic property of the food stuff the phase angle (φ) as the component of the impedance;   b) the phase angle (φ) over the same frequency spectrum for different characteristic properties, in particular for different food types as well as for different food age, differs in absolute values as well as in the first derivative and the second derivative;   c) the phase angle (φ) of fresh food stuff, in particular meat such as poultry, has a minimum in a given frequency spectrum whereas the phase angle (φ) of aged food stuff has no minimum in this given frequency spectrum;   d) the ratio of phases angles (φ) at two different frequencies (f) decreases with increasing age of the food stuff and is in particular used to check the quality of the food stuff before or at the beginning of the cooking process;   e) the phase angle has for vegetable a well defined maximum in a given frequency spectrum but at a different frequency for different vegetables as well as a different absolute value;   the phase angle has for different meat different absolute values at same frequencies.   
     
     
         11 . The method according to  claim 1 , comprising at least one (or an arbitrary combination) of the following steps or features:
 a) deriving from said detected impedance or component thereof information about characteristic property of the food stuff by calculating one or more electrical parameters (R; X; φ) of the food stuff from the electrical impedance (Z) or component thereof, and comparing said electrical parameters (R; X; φ) with a data base;   b) detecting, in another step during the cooking process and/or when the food stuff has been subjected to cooking already, the electrical impedance (Z) or the at least one component thereof of the food stuff again for determining the cooking progress and/or cooking temperature in the region of the food stuff;   c) wherein in particular a ratio of phase angles (φ) at two different frequencies (f) is calculated as a function of the temperature (T) of the food stuff;   d) deriving further to or as the information about the age or freshness of the food stuff an information on the estimated amount or concentration of bacteria in the food stuff.   
     
     
         12 . A food probe for inserting into a food stuff, being provided for use in deriving information about the food stuff in order to adjust one or more parameters of cooking the food stuff, comprising:
 an elongated rod made of a non-conductive material;   a front portion of the elongated rod, which front portion is provided for invading into the food stuff;   a first electrode made of a conductive material and arranged at the front portion of the rod;   a second electrode made of a conductive material and arranged at the front portion of the rod in a predetermined distance from the first electrode; and   a spike arranged at a front end of the rod; wherein:
 the first electrode and the second electrode are arranged serially along the longitudinal axis of the rod; 
 the food probe is connected or connectable to a voltage supply and a control circuit of a cooking oven or cooking appliance; and 
 a voltage can be applied between the first electrode and the second electrode, so that an electrical voltage is generated between and in the environment of the first electrode and the second electrode.